1. Field of the Invention
The present invention relates to a developer charging unit, a developing device, an image-forming apparatus, and a computer system.
2. Description of the Related Art
As one type of an image-forming apparatus, there is known, for example, an apparatus comprising a rotary-type developing unit. This rotary-type developing unit has a plurality of developing devices arranged radially about its axis of rotation. The developing devices are capable of developing a latent image formed on a photoconductor using developer, such as toner. When an image signal is sent from an external device such as a host computer, the image-forming apparatus makes the developing unit rotate about its axis of rotation in order to locate one of the plurality of developing devices in a developing position opposing the photoconductor. The apparatus forms a toner image by developing the latent image formed on the photoconductor, and then transfers the image onto an intermediate medium. A color image is formed by superimposing a plurality of toner images by sequentially changing the plurality of developing devices and repeating the above-mentioned developing and transferring processes.
In order to realize such functions as to develop a latent image formed on a photoconductor as mentioned above, a developing device has, for example: a developing roller, which serves as a developer bearing member for bearing toner; a toner reservoir; a toner supplying roller; and a restriction blade, which serves as a developer charging member and/or a thickness restricting member. The restriction blade is attached to the developing device through a support member for supporting the restriction blade and is capable of charging the toner bore by the developing roller. The restriction blade also abuts against the developing roller to restrict the thickness of the toner bore by the developing roller.
(1) In the developing device configured as above, since the restriction blade abuts against the developing roller, there is a possibility that the restriction blade will bend due to the load applied from the developing roller. Particularly, in case the developing roller and the restriction blade (or the support member for supporting the restriction blade) are supported at their end sections in the longitudinal direction, the degree of bending will become larger in the central section in the longitudinal direction of the restriction blade.
If such bending occurs in the restriction blade, there is a possibility that the pressing force of the restriction blade against the developing roller becomes uneven. Particularly, in the above-mentioned case, the pressing force will become weak at the central section in the longitudinal direction of the restriction blade.
Such an uneven pressing of the restriction blade may cause the toner charge to be uneven. Such unevenness in toner charge may cause problems such as deterioration in image, toner spill, and toner scatter.
Therefore, in order to make the toner charge even, a technique for reducing the unevenness in the pressing force of the restriction blade against the developing roller has been desired.
(2) Further, in some developing devices, end seals may be provided at each end section in the longitudinal direction of the restriction blade. These end seals function to prevent the toner from spilling out from between the frame and the circumferential surface of the developing roller.
The restriction blade and the end seals abut against the surface of the developing roller in order to achieve their functions described above. However, the characteristics of the end seals (for example, thickness, the properties of the material, etc.) is different from those of the restriction blade. Therefore, the end seals may have an influence on the pressing force of the restriction blade against the developing roller, and in some cases, the pressing force of the restriction blade against the developing roller becomes stronger at the end sections in the longitudinal direction of the restriction blade.
Such an uneven pressing of the restriction blade may cause the toner charge to be uneven. Such unevenness in toner charge may cause problems such as deterioration in image, toner spill, and toner scatter.
Therefore, in order to make the toner charge even, a technique for reducing the unevenness in the pressing force of the restriction blade against the developing roller has been desired.
(3) Further, as mentioned above, some developing devices have end seals provided in line with the restriction blade at each end section in the longitudinal direction of the restriction blade. These end seals function to prevent the toner from spilling out from between the housing and the circumferential surface of the developing roller.
The restriction blade and the end seals abut against the surface of the developing roller in order to achieve their functions described above. In order to make the end seals appropriately achieve their functions to prevent spilling of toner, it is necessary to press the end seals against the developing roller with a sufficiently large pressing force. On the other hand, if the pressing force of the restriction blade against the developing roller at the end sections, in the axial direction of the developing roller, of the restriction blade is equal to or larger than the strength of the pressing force of the end seals against the developing roller, then there is a possibility that the pressing force at the end sections of the restriction blade will become significantly greater than the other sections of the restriction blade.
Such an uneven pressing of the restriction blade may cause the toner charge to be uneven. Such unevenness in toner charge may cause problems such as deterioration in image, toner spill, and toner scatter.
Therefore, in order to make the toner charge even, a technique for reducing the unevenness in the pressing force of the restriction blade against the developing roller has been desired.
(4) Further, in some developing devices, it is necessary to keep the relative position of the restriction blade with respect to the developing roller constant. If there is a misalignment in the relative position, the thickness of the toner may become uneven. Such unevenness in thickness may bring about a problem that the degree of toner charge becomes uneven.
Therefore, in order to prevent such a problem from arising, a technique for preventing the misalignment in the relative position of the restriction blade with respect to the developing roller from occurring has been desired.